SR-25

The SR-25 (Stoner Rifle-25) is a semi-automatic sniper rifle designed by Eugene Stoner and manufactured by Knight’s Armament Company. The SR-25 employs a rotating bolt and a direct impingement gas system. It is loosely based on Stoner’s AR-10, rebuilt in its original7.62×51mm NATO caliber. Up to 60% of parts of the SR-25 are exchangeable with the AR-15 and M16—all but the upper and lower receivers, the hammer, the barrel assembly and the bolt carrier group. SR-25 barrels were first manufactured by Remington Arms with its 5R (5 grooves, rounded) rifling, with twist 1:11.25 (1 complete turn in 11.25 inches or 286 millimeters). The heavy 20 in (510 mm) barrel is free-floating, so hand guards are attached to the frontage of the receiver and do not touch the barrel.
First military procure was headed by the US Navy in the early 1990s; the first operational deployment and use of the SR-25 sniper rifle was with US Navy SEAL snipers supporting operations in Somalia 1993. The SR-25 enhanced match rifle utilizes the newer URX II Picatinny-Weaver rail system, instead of the older Mk 11 free-floating RAS, on the top of the receiver to accept diverse scope mounts or a carrying handle with iron sights. The match version is intended to shoot at an accuracy of 0.5 minutes of angle, which corresponds to 0.5-inch (13 mm) groups at 100 yards (91 m).

The Mk 11 Mod 0 system comes in 7.62 mm NATO caliber, and is intended for match-grade 7.62×51mm NATO ammunition. The Mk 11 system comprises the rifle, 20 round box magazines, QD (Quick Detachable) scope rings, and Leupold Mark 4 Mil-dot riflescope, Harris swivel-base bipod on a Knight’s mount, and QD sound suppressor, which is also manufactured by Knight’s Armament Co. Flip-up BUIS (Back up iron sights) are attached to the modified gas block and upper receiver.
The Mk 11 Mod 0 utilizes an Obermeyer 20 in (510 mm) match target barrel, along with a RAS (Rail Accessory System) fore-end made by KAC, consisting of an 11.35 in (288 mm) long match fore-end.

The RAS allows for quick attachment/detachment of MIL-STD-1913 components. The aluminum fore-end makes no contact with the barrel forward of the receiver, allowing for extreme accuracy. The Mk 11 Mod 0 has an empty weight of 15.3 lb (6.9 kg), and an overall length of 45.4 in (115 cm). The civilian version, using the longer 24 in (610 mm) match barrel, is guaranteed to produce groupings of less than 1 in (25 mm) at 100 yd (91 m), or 0.3 angular mil, using factory match loads.

During the Iraq War, the United States Marine Corps ordered 180 Mk 11 Mod 1 rifles. These were Mk 11s equipped with the upper receiver of the M110 Semi-Automatic Sniper System. The M110 upper gave the Mk 11 Mod 1 a URX modular rail system and a flash suppressor on the barrel. These saw limited use before they were phased out when the Marines chose to purchase the Mk 11 Mod 2, which was simply the USSOCOM and U.S. Navy designation for the complete M110 rifle.

The new SR-25 Enhanced Match (E.M.) Carbine is very similar to the KAC M110 Semi-Automatic Sniper System, though the M110 utilizes the newer URX Rail system, a length-adjustable fixed buttstock, and an integrated flash suppressor. Starting late 2011, USMC snipers will replace Mk 11 Mod 0 rifles with the M110 on a one-for-one basis.

Specifications

Wars: Afghanistan War, Iraq War, 2006 East Timorese crisis, 2nd Intifada
Variants: SR-25 Enhanced Match rifle, with 20 in (510 mm) barrel, SR-25 Enhanced Match Carbine, with 16 in (410 mm) barrel and M110 flash suppressor
Weight: Match Rifle 10.75 lb (4.88 kg), LwMatch 9.5 lb (4.3 kg), Carbine 7.5 lb (3.4 kg), Sporter 8.75 lb (3.97 kg)
Length: 1,118 mm (44.0 in)
Barrel length: Match Rifle 24 in (610 mm) also LwMatch & Sporter 20 in or 510 mm, Carbine 16 in or 410 mm)
Cartridge: 7.62×51mm NATO
Action: Gas-operated, rotating bolt
Feed system: 10 and 20-round detachable box magazine